document.write( "Question 1137318: Find the exact value of the expression:
\n" ); document.write( "sin(4pi/9)cos(pi/9) - cos(4pi/9)sin(pi/9) \n" ); document.write( "
Algebra.Com's Answer #755201 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "\"sin%284pi%2F9%29cos%28pi%2F9%29+-+cos%284pi%2F9%29sin%28pi%2F9%29+\"\r
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\n" ); document.write( "\n" ); document.write( "Use the following identity :\r
\n" ); document.write( "\n" ); document.write( "\"sin+%28s%29cos+%28t%29-cos+%28s%29sin+%28t%29=sin+%28s-t%29+\"\r
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\n" ); document.write( "\n" ); document.write( "in your case \"s=4pi%2F9+\"and \"t=pi%2F9\"\r
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\n" ); document.write( "\n" ); document.write( "\"sin%284pi%2F9%29cos%28pi%2F9%29+-+cos%284pi%2F9%29sin%28pi%2F9%29+=sin+%283pi%2F9++%29+\"\r
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\n" ); document.write( "\n" ); document.write( "\"sin%284pi%2F9%29cos%28pi%2F9%29+-+cos%284pi%2F9%29sin%28pi%2F9%29+=sin+%28pi%2F3++%29+\"\r
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\n" ); document.write( "\n" ); document.write( "Use the following identity : \"sin++%28+pi%2F3+%29=+sqrt%283%29%2F2\"\r
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\n" ); document.write( "\n" ); document.write( "\"sin%284pi%2F9%29cos%28pi%2F9%29+-+cos%284pi%2F9%29sin%28pi%2F9%29+=sqrt%283%29%2F2\"\r
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